CINCINNATI -- Usually a haven for offense, the Reds' return to Great American Ball Park appeared to be the right tonic for their weary bats.

Or so we thought.

Notching just three singles in a 7-1 series-opening loss to the Nationals on Tuesday, including two infield hits, Cincinnati has dropped four of its last six games. In each of the four losses, the offense scored one run or less.

"I came over here and got spoiled," said first baseman Scott Hatteberg, whose seventh-inning sacrifice fly scored the Reds' only run. "This is a pretty good offensive team. I think we have hit a bit of a skid on the road trip a little bit and today. But I don't foresee it being a problem. I think we can get out of it anytime."

On the recently completed 2-3 road trip, the Reds scored seven and nine runs in the wins -- so it's not time to sound the alarms yet. They also remain in first place by a half-game over St. Louis in the National League Central division.

Pitching into the seventh inning, Nationals starter Tony Armas Jr. (3-2) made sure Cincinnati's bats stayed stifled. Armas allowed just two hits but none between Edwin Encarnacion's leadoff single in the second inning and Felipe Lopez's infield hit behind second base leading off the seventh.

"You got to give him credit," said Hatteberg, sporting an ice wrap on his right wrist after taking a Nick Johnson line drive in the seventh. "He had us off balance. He's not overpowering but he used his stuff well."

With five home runs on the night, including two by Jose Guillen, Washington had no such issues. Reds starter Brandon Claussen (2-4) coughed up three of the long balls during his 5 1/3 innings while tying a career high with 11 hits allowed.

A leadoff double by Royce Clayton, followed by a pair of blooped broken-bat singles by Marlon Byrd and Jose Vidro gave the Nationals their first run.

The rest of the runs weren't on cheapies.

Ryan Zimmerman took Claussen deep to center field for a solo homer in the fourth. Guillen led off the sixth with a first-pitch homer to right field. Two batters later, Matthew LeCroy added a solo shot to left field that made it 4-0 and drew boos from 16,716 fans. Claussen was pulled after Clayton followed LeCroy with a single.

"With the stuff he has, he needs to get guys out as early as he can as possible," Reds manager Jerry Narron said. "At times tonight, I thought he threw really well. But you have to be consistent at this level to be successful."

Guillen's two-run homer off Matt Belisle in the seventh made it 6-0, but Cincinnati still had a chance to hang in the game.

Armas followed Lopez's leadoff hit by walking Adam Dunn on four pitches and hitting Edwin Encarnacion with a pitch to load the bases.

Drawing lefty reliever Joey Eischen, Hatteberg worked a 3-0 count before falling to a full count on a borderline strike two call. The next pitch was smoked to right field, but caught by Guillen. Lopez tagged up and scored easily.

After Austin Kearns struck out, Brandon Phillips loaded the bases again with an infield hit to third base. Jason LaRue grounded into a fielder's choice play to end the Reds' lone threat.

"We knocked on the door," Hatteberg said. "That would have been pivotal if we pushed them across. It was obviously a momentum swing their way when we couldn't capitalize. We had a couple of balls hit, no luck."

Washington's fifth, and final, long ball put the proper exclamation point on this thumping. Alfonso Soriano tattooed an impressive solo homer off Brian Shackelford that cleared the batters' eye beyond the center-field wall. Estimated at 492 feet, Soriano's homer was the fourth longest on record since Great American Ball Park opened in 2003.

The Nationals' five homers also tied the Great American Ball Park record for home runs by an opponent, done five previous times. At its home in RFK Stadium, Washington has notched just 13 homers while batting .227.

Any road ballpark appears to serve the Nationals' offensive tonic. They have a .271 average and 29 homers on the road.

That's easier to understand since RFK is known as a hitters' graveyard.

Narron had no answer for what's ailing his club's bats.

"We got beat, as simple as that," was all he said.